为什么pclose（3）不等待shell命令终止

I want to test the pclose(3) whether it will wait the shell command terminate.I write two little shell program.

我想测试一下pclose(3)是否会等待shell命令终止。我写了两个小shell程序。

//a.sh
#!/bin/bash
sleep 3

//b.sh
#!/bin/bash
echo "something"
sleep 3

c program:

//ptest.c

#include <stdio.h>
#include <sys/wait.h>

int main(int argc, char **argv) {
    char *filename = argv[1];
    char *mode = argv[2];
    FILE *fl = popen(filename, &mode);
    int t = pclose(fl);
    if(WIFEXITED(t)) {
        printf("exit status:%d\n", WEXITSTATUS(t));
    }
    return 0;
}

then, compile: $ gcc -o ptest ptest.c

然后,编译:$ gcc -o ptest ptest.c

next run the ptest(my computer is Ubuntu 12.04.3 LTS）:

接下来运行ptest(我的电脑是Ubuntu 12.04.3 LTS):

$ ./ptest "sh a.sh" r
$ exit status:0

this test will wait the shell terminate and output exit status 0.However when I run the ptest as following form:

此测试将等待shell终止并输出退出状态0.但是当我按以下形式运行ptest时:

$ ./ptest "sh b.sh" r
$ exit status:141

this time, ptest don't wait shell program and terminate itself immediately， I just add an echo statement before the sleep, But the result was different. I don't know why .

这次,ptest不要等待shell程序并立即终止自己,我只是在睡眠前添加一个echo语句,但结果却不同了。我不知道为什么。

1 个解决方案

#1

exit status:141 is a SIGPIPE error. It is well explained in this question Why exit code 141 with grep -q?

退出状态:141是SIGPIPE错误。在这个问题中有很好的解释为什么用grep -q退出代码141?

The issue is that your b.sh script tries to write to the pipe, but nobody is reading this pipe in your C program.

问题是您的b.sh脚本尝试写入管道,但没有人在您的C程序中读取此管道。

#1